I was recently investigating a bug regarding the facets selection dialog, where pressing cancel does not revert the changes made on the page, I found that the method cancelPressed in class: org.eclipse.wst.common.project.facet.ui.internal.FacetsSelec tionDialog has a stub to do implementation of this.
Before taking any action on this I thought it would be prudent to contact you and ask if there is a plan for this item or if it has an implementation in another code base that can be ported here...

This is expected. The dialog is directly editing the working copy shared with the wizard. Reverting changes made in the dialog is not practical. There was an attempt a few years ago to implement this, but due to complexity, issues that could not be resolved and relatively minor benefit, the project was abandoned.

Yes, On investigating the code I see that having cancel revert changes is indeed impractical, however it seems that having a cancel button that essentially does the same thing as the Ok button is misleading. If possible, I would suggest the cancel button be removed in this case, or disabled, then it would be obvious to the user whatever changes are made will be applied.

I'm helping Scott out here locally decide what to do in this case. and I like his suggestion. Can we look into changing the dialog code to disable the "Cancel" button" if invoked from the Project Facet wizard? Seems like an easy fix, and makes it more obvious to the user what will happen. We'll look into it and post a bugzilla if this can be done easily